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The Einstein–Szilárd Letter
In August 1939, two American physicists, Leó Szilárd and Eugene Wigner wrote the Einstein–Szilárd letter, which stated the threat of an "extremely powerful bombs of a new type" -
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Manhattan Project
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The First S-1 Uranium Commitee Meeting
Roosevelt had Lyman Briggs from the National Bureau of Standards hold a meeting with Szilard and Wigner in October 21 where they reaffirmed their worries about uranium bombs. -
The MAUD Committee
The MAUD Committee (Military Application of Uranium Detonation) is established by Henry Tizard to investigate possibility of an atomic bomb.
The picture shown is the first report of the MAUD committee. -
Uranium-235
Franz Simon reports to MAUD that uranium-235 can be separated by using gaseous diffusion. Giving the cost estimates and technical specifications, James Chadwick realizes that "a nuclear bomb...is inevitable."
The picture shows the proccess of gaseous diffusion of Uranium-235. -
Roosevelt Gives the Go Ahead
Roosevelt signs an executive order that creates a committee for research on Uranium 235. -
Bomb Research
Vannevar Bush, the head of the Office of Scientific Research and Development, briefs Roosevelt and Vice President Henry A. Wallace on the state of atomic bomb research. Roosevelt instructs Bush to find out if a bomb can be built and at what cost. Bush receives permission to explore construction needs with the Army. The man in the picture to the left is Vannevar Bush. -
Atomic Bomb is Feasible
After 3 National Academies of Sciences' research, they agree through a MAUD report that an atomic bomb is feasible. -
Bush Sends the News
Bush forwards the National Academy of Sciences report to the President. -
Manhattan Engineering District
FDR authorizd the Manhattan Engineering District for the creation of the atomic bomb. The Manhattan District was the army component of this program. This would later be called the 'Manhattan Project'.
The picture is the unofficial emblem of the Manhattan Engineering District. -
Pearl Harbor
The Japanese attack Pearl Harbor to neutralize the U.S. Pacific Fleet, so they could protect Japan's advance into Malaya and the Dutch East Indies to get oil and rubber. -
The Production Begins
Roosevelt responds to Bush's November 27 report and approves production of the atomic bomb. -
The Manhattan Project
Colonel Leslie Groves is placed in charge of the Manhattan Project. J. Robert Oppenheimer becomes the Project's Scientific Director.
The picture is the official insignia of the Manhattan Project. -
Selection of Los Alamos as a Test Site
Groves selects Los Alamos, New Mexico, as a bomb lab. This lab is codenamed Project Y which has Oppenheimer as the lab manager. -
First Nuclear Developments
Scientist Enrico Fermi achieves the first self-sustained nuclear chain reaction in Chicago. This picture is a drawing of the nuclear reactor. -
Construction of Y-12 Reactor
Construction begins for the Y-12 reactor at Oak Ridge, Tennessee. The reactor involves massive electromagnetic separators which will be used for enriching the uranium. Different types of reactors would later be built at Oak Ridge. To the left is a picture of the electromagnetic separators. -
FDR's Death
President Franklin Roosevelt dies and Harry Truman becomes the President. -
Japan Becomes the Target
The Military Policy Committee selects Japan as the primary target for future bombings after Japan's refusal to surrender. -
Testing Bomb Types
Different types of nuclear bombs are scaled and tested at the Los Alamos Laboratory in New Mexico. Scientists are preparing an implosion-type bomb at Los Alamos. -
The Warning
Leo Szilard tries to warn President Truman about the dangers of the atomic weapon. -
Selecting the Cities
The Target Committee of the Manhattan Project selected four cities as posssible targets for the atomic bomb. They are; Kyoto, Hiroshima, Kokura, and Niigata. -
Germany's Defeat
On April 30, 1945, the Reichstag was captured, signalling the military defeat of Third Reich. -
Trinity Bomb Test
An implosion-type atomic bomb is tested at Alamogordo, New Mexico. This test is called the Trinity test. -
The Potsdam Conference
A conference was held to administer Nazi Germany's punishment after the war. During this conference, Truman tells Stalin of "a new weapon of unusually destructive force." Stalin already knew about it due to his spies. -
Rejection
The Potsdam Conference was broadcasted to Japan, threatening the total destruction of Japan unless the Imperial Japanese Government submit to unconditional surrender. The Japanese did not surrender. -
Bombing of Hiroshima
The Enola Gay, with pilot Paul Tibbets and bombardier William Parsons, drops the Little Boy, a pistol-type nuclear bomb, over Hiroshima. -
Bombing of Nagasaki
Pilot Charles Sweeney and weaponeer Frederick Ashworth drop the Fat Man, an implosion-type nuclear bomb, on Nagasaki. The bomb was originally meant for the city of Kokura, but cloud cover caused the bombing to be relocated to Nagasaki. -
World War II Ends
The massive World War II ends with the capture of Japan and Germany. -
Manhattan District Gets Abolished
Since WWII ended, the atomic program was no longer needed for war. The Manhattan Project ceased to exist on December 31, 1946, but the Manhattan District would remain, until it too was abolished on August 15, 1947.
